SYSTEM AND METHOD FOR ENVELOPE TRACKING POWER SUPPLY

• US 20130021827A1
• Filed: 07/22/2011
• Published: 01/24/2013
• Est. Priority Date: 07/22/2011
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Ye, Zhong
• Granted Patent: US 9,496,828 B2
• Time in Patent Office: Days
• US Class Current: 363/17
• CPC Class Codes: H03F 1/025 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/3241 using predistortion circuits H03F1/3211, H03F1/3217 take precedence
• CPC Class Codes: H03F 2200/507 A switch being used for switching on or off a supply or supplying circuit in an IC-block amplifier circuit
• CPC Class Codes: H03F 2200/511 Many discrete supply voltages or currents or voltage levels can be chosen by a control signal in an IC-block amplifier circuit
• CPC Class Codes: H03F 2200/555 A voltage generating circuit being realised for biasing different circuit elements
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers
• CPC Class Codes: H03F 3/245 with semiconductor devices only

Abstract

An envelope tracking power supply has a multiple-output DC/DC converter, a switch bank, an output voltage selector and an output filter. The DC/DC converter has an alternating current generating portion and a full rectifying portion. The alternating current generating portion, typically a LC circuit, can receive an input voltage and operate at zero voltage switching. The full rectifying portion includes at least one secondary winding and one voltage doubler output. Each voltage doubler has a first transistor, a second transistor, a first capacitor and a second capacitor. The transistors used as rectifier devices allow currents to flow bi-directionally and sink and source the currents from and to output capacitors to keep their voltage balance. Secondary windings and output capacitors are connected in series respectively. A switch bank selects a desired voltage from the series connected capacitors and connects it to the output filter. The switch bank receives an envelope tracking command from the voltage selector and provides a step voltage to the output. The output voltage is changed at switching speed to track a high bandwidth envelope signal.

Claims

1. A transmission device comprising:

a signal source operable to generate a command signal and a source signal;

a voltage supply circuit including an alternating current generating portion and a full rectifying portion, said voltage supply circuit being operable to generate an envelope tracking voltage based on the command signal; and

a transmitting portion operable to transmit a signal based on the source signal and the envelope tracking voltage,

wherein said alternating current generating portion is to receive the command signal and includes a first input transistor, a second input transistor and a primary winding,

wherein said first input transistor and said second input transistor are operable to generate a primary alternating current through said primary winding based on the command signal,

wherein said full rectifying portion includes a secondary winding and a voltage doubler having a first transistor, a second transistor, a first capacitor and a second capacitor,

wherein said secondary winding is operable to generate a secondary alternating current based on the primary alternating current,

wherein said first transistor is operable to conduct a first current in a first direction to the first capacitor based on a positive portion of the secondary alternating current,

wherein said first capacitor is operable to store a first charge based on the first current,

wherein said second transistor is operable to conduct a second current in a second direction to said second capacitor based on a negative portion of the secondary alternating current, and

wherein said second capacitor is operable to store a second charge based on the second current.

2. The transmission device of claim 1,

wherein said voltage supply circuit further comprises a LLC converter including a first inductor, a second inductor and a capacitor, said LLC converter being operable to generate an AC current with zero-voltage switching,

wherein said first input transistor and said second input transistor are operable to generate the primary alternating current through said primary winding with zero-voltage switching.

3. The transmission device of claim 1,

wherein said full rectifying portion further includes a second secondary winding and a second voltage doubler having a third transistor, a fourth transistor, a third capacitor and a fourth capacitor, said second secondary winding being connected in series with said secondary winding, said third capacitor being connected in series with said first capacitor, said fourth capacitor being connected in series with said second capacitor, and

wherein said first capacitor, said second capacitor, said third capacitor and said fourth capacitor are connected in series to form a capacitor string and to provide a stepped output voltage.

4. The transmission device of claim 3,

wherein said voltage supply circuit further comprises a baseline voltage generating portion operable to generate a baseline voltage and including a center-tapped secondary winding and a full-wave rectification circuit having a first rectifier transistor, a second rectifier transistor and a baseline capacitor,

wherein said center-tapped secondary winding is operable to generate a baseline alternating current based on the primary alternating current,

wherein said first rectifier transistor is operable to conduct a first baseline current in the first direction passing said baseline capacitor based on a positive portion of the baseline alternating current,

wherein said second rectifier transistor is operable to conduct a second baseline current in the second direction passing said baseline capacitor based on a negative portion of the baseline alternating current, and

wherein said baseline capacitor is operable to store a baseline charge based on the first baseline current and the second baseline current.

5. The transmission device of claim 4,

wherein said voltage supply circuit further comprises a switch bank including a plurality of bidirectional switches and a baseline switch,

wherein said switch bank is operable to generate an output based on the baseline voltage, the voltage of said first capacitor, the voltage of said second capacitor, the voltage of said third capacitor, the voltage of said fourth capacitor or a combination thereof,

wherein said baseline switch is operable to generate the output based only on the baseline voltage only, and

wherein said plurality of bidirectional switches and said baseline switch are connected to have a common ground.

6. The transmission device of claim 5, wherein said voltage supply circuit further comprises an output filter arranged to receive the output of said switch bank, said output filter including an output capacitor, an output inductor and a damping network.

7. The transmission device of claim 5, wherein said voltage supply circuit further comprises a selector operable to output gate driver signal to turn on one of said plurality of bidirectional switches to generate the output of said switch bank.

8. The transmission device of claim 4, wherein, when an excess charge is stored on one of said first capacitor and said second capacitor, said baseline capacitor is arranged to receive the excess charge by way of a coupling of said secondary winding and said center-tapped secondary winding.

9. The transmission device of claim 8, wherein said alternating current generating portion is operable to modify the primary alternating current through said primary winding based on the excess charge on said baseline capacitor.

10. The transmission device of claim 9, wherein, when said baseline capacitor has received an excess charge from one of said :

first capacitor and said second capacitor, the other of said first capacitor and said second capacitor is arranged to receive the excess charge from said baseline capacitor by way of the coupling of said secondary winding and said center-tapped secondary winding.

11. The transmission device of claim 1, wherein said voltage supply circuit further comprises a controller operable to provide first gate driver signals, based on the baseline voltage, to said first input transistor and said second input transistor to regulate the baseline voltage and to provide second gate driver signals to said first transistor and said second transistor to control the first current and the second current to achieve synchronized rectification.

12. The transmission device of claim 11, wherein said controller comprises a first gate driver circuit operable to provide the first gate driver signals and a second gate driver circuit operable to provide the second gate driver signals.

13. The transmission device of claim 1,

wherein said secondary winding has a positive integer n turns,

wherein said full rectifying portion further includes M voltage doublers,

wherein M is a positive integer greater than 1,

wherein each M voltage doubler includes a respective first transistor, a respective second transistor, a respective first capacitor and a respective second capacitor,

wherein each M voltage doubler is connected to said secondary winding such that there are an equal number of turns of said secondary winding for said voltage doubler and for each of said M voltage doublers, and

wherein said secondary winding is further operable to generate equal secondary alternating currents based on the primary alternating current for each of said M voltage doublers, respectively,

wherein each said respective first transistor is operable to conduct an equal first respective current in a first respective direction to each said respective first capacitor based on the positive portion of the secondary alternating current,

wherein each said respective first capacitor is operable to store an equal first respective charge based on the respective first currents,

wherein each said respective second transistor is operable to conduct an equal second respective current in a second respective direction to each said respective second capacitor based on the negative portion of the secondary alternating current, and

wherein each said respective second capacitor is operable to store an equal respective second charge based on the respective second currents.

14. A method of generating multiple output voltages, said method comprising:

receiving, via an alternating current generating portion having a power transformer that includes a primary winding, an input voltage;

generating a primary alternating current through the primary winding of the power transformer;

generating, via a secondary winding, a secondary alternating current based on the primary alternating current;

providing, via a rectification circuit, a positive portion of the secondary alternating current across a first output capacitor to generate a first output voltage;

providing, via the rectification circuit, a negative portion of the secondary alternating current across a second output capacitor to generate a second output voltage; and

modulating, via a feedback circuit, the primary alternating current based on at least one of the first output voltage and the second output voltage,

wherein the rectification circuit, the first output capacitor and the second output capacitor are arranged such that the rectification circuit is operable to conduct current bi-directionally to sink the positive portion of the secondary alternating current to the first output capacitor, to source the positive portion of the secondary alternating current to the first output capacitor, to sink the negative portion of the secondary alternating current to the second output capacitor, to source the negative portion of the secondary alternating current to the second output capacitor.

15. The method of claim 14,

wherein said providing, via a rectification circuit, a positive portion of the secondary alternating current across a first output capacitor to generate a first output voltage comprises providing, via a second secondary winding and a second voltage doubler having a third transistor, a fourth transistor, a third capacitor and a fourth capacitor, the second secondary winding being connected in series with the secondary winding, the third capacitor being connected in series with the first capacitor, the fourth capacitor being connected in series with the second capacitor, and

wherein the first capacitor, the second capacitor, the third capacitor and the fourth capacitor are connected in series to form a capacitor string and to provide a stepped output voltage.

16. The transmission device of claim 15, further comprising:

generating a baseline voltage via a baseline voltage generating portion including a center-tapped secondary winding and a full-wave rectification circuit having a first rectifier transistor, a second rectifier transistor and a baseline capacitor,

wherein the center-tapped secondary winding is operable to generate a baseline alternating current based on the primary alternating current,

wherein the first rectifier transistor is operable to conduct a first baseline current in the first direction passing the baseline capacitor based on a positive portion of the baseline alternating current,

wherein the second rectifier transistor is operable to conduct a second baseline current in the second direction passing the baseline capacitor based on a negative portion of the baseline alternating current, and

wherein the baseline capacitor is operable to store a baseline charge based on the first baseline current and the second baseline current.

17. The method of claim 16, wherein when an excess charge is stored on one of the first capacitor and the second capacitor, the baseline capacitor is arranged to receive the excess charge by way of a coupling of the secondary winding and the center-tapped secondary winding.

18. The method of claim 17, further comprising modifying, via the alternating current generating portion, the primary alternating current through the primary winding based on the excess charge on the baseline capacitor.

19. The method of claim 18, wherein when the baseline capacitor has received an excess charge from one of the first capacitor and the second capacitor, the other of the first capacitor and the second capacitor is arranged to receive the excess charge from the baseline capacitor by way of the coupling of the secondary winding and the center-tapped secondary winding.

20. A method of generating a tracking voltage based on an input signal, said method comprising:

providing a voltage supply circuit comprising and alternating current generating portion, and a full rectifying portion, the alternating current generating portion being operable to receive an input voltage and including a first input transistor, a second input transistor and a primary winding, the first input transistor and the second input transistor being operable to generate a primary alternating current through the primary winding based on the input voltage, and the full rectifying portion including a secondary winding and a voltage doubler having a first transistor, a second transistor, a first capacitor and a second capacitor, the secondary winding being operable to generate a secondary alternating current based on the primary alternating current, the first transistor being operable to conduct a first current in a first direction passing the first capacitor based on a positive portion of the secondary alternating current, the first capacitor being operable to store a first charge based on the first current, the second transistor being operable to conduct a second current in a second direction passing the second capacitor based on a negative portion of the secondary alternating current, the second capacitor being operable to store a second charge based on the second current;

receiving, via a selector, the input signal;

generating, via the selector, a voltage selection signal;

selecting, via a switch bank, a desired voltage from the voltage supply circuit based on the voltage selection signal;

outputting, via the voltage supply circuit, the desired voltage as an output voltage; and

filtering, via an output filter, the output voltage.